Southern Kansas now faces a bigger risk of a damaging earthquake than southern California.
That’s the finding of a yearly risk assessment released Monday by the U.S. Geological Survey, the first such report covering the once seismically placid central states.
Maps attached to the report show a pocket of northern Oklahoma and southern Kansas where the risk of a damaging quake is estimated as high as 10 to 17 percent in the next year.
That’s bigger than Los Angeles County, where the risk is 2 to 5 percent and comparable to the shakiest parts of the San Francisco Bay area.
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The new report gauges earthquakes’ potential for damage using the Modified Mercalli Intensity scale, a 12-point system that measures the effect of quakes. It is separate from the better-known Moment Magnitude scale that measures energy release.
“The chance of having Modified Mercalli Intensity VI or greater (damaging earthquake shaking) is 5-12 percent per year in north-central Oklahoma and southern Kansas, similar to the chance of damage caused by natural earthquakes at sites in parts of California,” the report concludes.
“The first thing I’d say is don’t panic,” advised George Choy, a seismologist with the USGS earthquake center in Colorado.
People in California have lived with these hazard maps for a couple of decades, and nobody’s moving around or panicking.
George Choy, USGS seismologist
“People in California have lived with these hazard maps for a couple of decades, and nobody’s moving around or panicking. What the short-term map does is give you an idea of what you should be prepared for.”
The report shows that northern Oklahoma and southern Kansas have experienced just short of 6,000 earthquakes of magnitude 2.7 or more in the past two years.
Choy said it’s important to look at the Mercalli scale instead of just magnitude to assess the risk of damage.
“The present bedrock of the central and eastern U.S. is older, more solid than along the West Coast, and it transmits energy to greater distances,” he said. “For a given magnitude, an earthquake in the east (and central U.S.) could be felt to much greater distances than along the West Coast.”
While California quakes are caused by natural movement of geologic plates and are fairly predictable over a long-term basis, the spike in seismic activity in the midcontinent is primarily attributed to oil and gas industry activity.
The USGS felt as if it needed a new hazard map because “what’s happened in the central United States is that there were pockets of seismicity that were occurring suddenly at unnatural rates,” Choy said.
There’s a short-term hazard which hasn’t been mapped before, and we had to come up with ways to take that into account.
George Choy, USGS seismologist
“We have a whole history of seismicity in California … whereas in the central United States, we only have a short history, and some of these places only a few years,” he said. “There’s a short-term hazard which hasn’t been mapped before, and we had to come up with ways to take that into account.”
While many people blame the petroleum industry’s “fracking” – subsurface fracturing that frees trapped pockets of oil and gas – most scientists say the actual problem is disposal of wastewater that comes up with the oil. Every barrel of oil pumped in southern Kansas generates about 16 barrels of wastewater.
Because the wastewater is too salty and oil-contaminated for economical surface disposal, producers get rid of it by injecting it deep underground. Scientists say that can upset the balance of forces in deep-rock formations and trigger earthquakes.
Since March 2015, the Kansas Corporation Commission has placed limits on the locations and disposal amounts of wastewater injection to try to reduce the hazard.
The KCC is in the process of considering an expansion of the areas where wastewater disposal is limited, which could bring the restrictions into eastern Kingman and western Sedgwick counties as far north as Cheney.
Oklahoma initially resisted such limitations but is now catching up, Choy said.
Choy recommended that communities affected by quakes may want to start having more frequent inspections of critical facilities.
He said some may also consider changes in their building codes, but that’s a hard decision because the codes take time to take effect, and quakes may just be a short-term risk that will be reduced by cutting back wastewater disposal.
For individuals, he suggested educating “yourself on how to prepare your house, what to do if an earthquake does occur.”
Some common tips on preparing your home for earthquakes.
▪ Pictures – Avoid hanging pictures over the bed, or secure them tightly with screws into the wall studs.
▪ Chimneys – Unreinforced masonry chimneys can fall through roofs and ceilings. Have a contractor look over a chimney to see whether it can be strengthened. If you’re anywhere near the fireplace when an earthquake hits, seek shelter in a safer room until it’s over.
▪ Natural gas connections – Best practice is to replace rigid lines with flex lines and strap the equipment in place.
▪ Tall bookshelves – They’re top-heavy and can easily tip over in a quake. Bolt or strap standing shelves to the wall studs.
▪ Electronic equipment – Big-screen TVs, computer monitors and the like can easily fall over in a quake, wrecking the equipment and potentially injuring someone nearby. Tie the equipment to the table or stand with nylon straps.
▪ Knick-knacks and heirlooms – There are special waxlike adhesives, known as museum putty, made for sticking valuable items to shelves so they don’t fall and break. Museum putty is marketed under trade names such as QuakeHold and Quake Secure. While it’s not widely stocked in Kansas stores, you can order it online, or a hardware or building supply store can get it for you.
▪ Pantry shelves – Run a secured wire across the front of pantry shelves to keep the food in place. With wooden shelves, you can screw a board across the front to create a lip that will prevent food from falling out.
▪ Cabinets and hutches – Use child-safe locks to keep the doors closed so glasses and wedding china don’t wind up in shattered shards on the floor.
▪ Shoes – Keep an old pair of sturdy-soled shoes under the edge of your bed. After an earthquake, you may have to walk out over broken glass or other debris on the floor.
More tips on earthquake safety and preparedness are available online from the Federal Emergency Management Agency at www.ready.gov and from the California Office of Emergency Services, www.calema.ca.gov/.